int strStr(char * haystack, char * needle)
{
    if(strlen(needle) == 0 || strlen(haystack) < strlen(needle))
    {
        return -1;
    }
    int flag =0;
    int i=0;
    int j=0;
    for(i;i<=strlen(haystack) - strlen(needle);i++)
    {
        if(*(haystack+i) == *needle)
        {
            flag =i;
            int k=i;
            for(j=0;j<strlen(needle);k++,j++)
            {
                if(*(haystack+k) != *(needle+j))
                {
                    break;
                }
            }
            if(j == strlen(needle))
            {
                return flag;
            }
        }
    }
    return -1;
}